This invention relates to a mounting structure for mounting a nozzle on a pressure vessel, and more particularly it relates to a structure for mounting a cylindrical nozzle body on a pressure vessel body having an internal lining for corrosion resistance or other purposes, said nozzle body being made of a material which cannot be welded to the pressure vessel body.
In the case where a pressure vessel has a lining of such a nonferrous metal material incapable of being welded to a steel vessel, for example titanium, an inner surface of the nozzle to be mounted on the pressure vessel should be made of a corrosion-resistant material or the like.
A conventional nozzle mounting structure for the this purpose, as shown in FIG. 1, is formed by welding, to a pressure vessel body 1, a nozzle body 2 of the same material as the vessel body as designated 3, covering an inner surface of the nozzle body 2 with a liner 4 of a special material and welding the liner 4 to a liner 5 adhered to an inner surface of the pressure vessel body side 1 as designated 6. Because of the difference in coefficient of thermal expansion between the liner 4 on the nozzle side and the nozzle body 2, a crack 7 can occur at a welding joint portion 6 between the nozzle side liner 4 and the body side liner 5 or the body side liner 5 can rise to form a clearance gap 8 with respect to the vessel body as seen in FIG. 2 through of repeated transition between a high temperature state existing during operation and a low temperature state existing during shutdown. This results not only in corrosion and other unfavorable phenomena but also in a need for periodic replacement of the nozzle side liner 4 since a corrosive fluid flows inside the nozzle side liner 4 and its leading edge portion 9 is worn out quickly due to erosion and corrosion.
The above structure wherein the welding portion 6 is given sufficient strength is also disadvantageous in that replacing only the nozzle side liner is very difficult, a gasket seat 11 is necessary at a joint portion 10 with an opposing flange of the nozzle body, and the liner 4 is thus complex in structure, resulting in an increase in manufacturing cost, difficulty in assembling procedure, etc.